<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
<title></title>
</head>

<body>
<form name="form">
    <label>请选择表情：</label>
    <select name="expression" onChange="showHead(this)">
        <option value="images/01.png">发呆</option>
        <option value="images/02.png">睡觉</option>
        <option value="images/03.png">难过</option>
        <option value="images/04.png">调皮</option>
        <option value="images/05.png">装酷</option>
    </select>
</form>
<div id="box"><img src="images/01.png"></div>
<script type="text/javascript">
    function showHead(obj){
        var imgSrc=obj.value;
        var box=document.getElementById("box");
        box.innerHTML="";
        var img=document.createElement("img");
        img.src=imgSrc;
        box.appendChild(img);
    }
</script>
</body>
</html>
